Melting furnace

ABSTRACT

A melting furnace constituted by a crucible supported at its periphery by a gas-tight refractory structure forming a combustion chamber having a furner fitted at the bottom and a duct for evacuating burnt gases disposed at one of its sides.

United States atem 1191 Berger Jan. 14, 1975 [5 MELTING FURNACE2,606,016 8/1952 Lindh et a1. 266/16 [75] Inventor: Paul C. Berger,Paris, France FOREIGN PATENTS OR APPLICATIONS 73] Assignee; FLUXO pantinFrance 1,280,478 10/1968 Germany 266/33 R [22] Filed: 1973 PrimaryExaminer-Gerald A. Dost 21 App], 391,02 Attorney, Agent, or Firm-Lane,Aitken, Dunner &

Ziems [52] U.S. Cl. 266/33 R, 266/16 51 Int. Cl. F27b 14/00 [57]ABSTRACT 58] Field of Search 266/15, 16, 19, 24, 33 R, A meltmg furnaceconsumed y a crumble Supported 2 /33 3 39; 432/ 5 at its periphery by agas-tight refractory structure forming a combustion chamber having afurner fitted [56] References Ci at the bottom and a duct for evacuatingburnt gases UNITED STATES PATENTS disposed at one of its sides.

1,896,951 2/1933 Hahn 266/16 3 Claims, 2 Drawing Figures MELTING FURNACEThe present invention concerns a melting furnace constituted by acrucible supported at its periphery by a gas-tight refractory structureforming a combustion chamber having a burner fitted at the bottom and aduct for evacuating burnt gases disposed at one of its sides.

When it is required to shield the materials to be heated against contactwith the flames or with the gases of combustion, use is generally madeof crucible furnaces. Thus, such furnaces are used for melting whitemetals so as to prevent them from being oxidized.

However, crucible furnaces suffer from numerous disadvantages. Thestructure forming the combustion chamber is usually not cooledefficiently, and the intense heating-up of the refractory materialforming the chamber leads to its becoming worn. Very often cracks can beseen it its walls and it has to be replaced. The furnace cannottherefore be used during the repair operations, and production isreduced. Furthermore, the considerable heat dissipated from thesupporting structure causes considerable trouble to the workmenoperating around the furnace and mades their task very uncomfortable.

On the other hand a considerable volume of gas is released when thefurnace charge melts. Since these gases are exhausted into the workshopand so causes pollution, it is necessary to provide hoods above thefurnaces and this increases the capital cost of the installation.

An object of the present invention is to overcome these disadvantagesand to provide a melting furnace, the walls of the supporting structureof which are cooled to an extent such that the useful life of therefractory material is increased and the temperature of the areasurrounding the furnace is reduced. Another object of the invention isto suppress pollution by removing the gases released from the moltenmaterial as soon as they form, without the need for fitting a hood.

These objects are achieved by the melting furnace of this inventionwhich is characterized by a double wall which defines a chamberextending at least around and above the refractory supporting structure,the chamber being connected with a duct fitted with an extraction fanand having two air inlets, one being annular and extending around theperiphery of the crucible and the other extending through the side wallof the chamber.

By means of this arrangement the walls of the supporting structure arecooled since they are surrounded by a chamber in which fresh aircirculates after having entered through the lateral inlet. The side wallof the chamber, likewise cooled by the stream of fresh air, provides thesupporting structure with thermal insulation and therefore limits therise in temperature of the surrounding area. Furthermore, since thechamber has an air inlet extending around the periphery of the crucible,the gases formed within the crucible are drawn into this inlet anddirected to the exhaust duct by the fan.

The cooling of the walls of the supporting structure and the exhaustingof the polluting gases are thus achieved simultaneously by a simplemeans consisting only ofa fan and ofa chamber having two air inlets,this means also offering the advantage of being less costly on accountof the absence of a hood.

The chamber advantageously includes a lateral outer wall which rests ona protruding part of the base of the supporting structure and an annularcover which has an outer downwardly extending lip which caps the lateralwall, and an inner downwardly extending lip which terminates near theperiphery of the crucible.

Since the chamber rests on a protruding portion of the base of thesupporting structure, it canbe rapidly assembled in view of the factthat it can be placed in position without the need for providing asupplementary structure for supporting it.

The inner lip of the cover which limits the size of the air inletdisposed at the periphery of the crucible, enables the opening to bedisposed in a uniform manner around the crucible, and directs theopening towards the interior of the crucible.

All the gases liberated from the crucible charge are thus drawn out bythe fan.

. The outer lip of the cover on the other hand enables I I travelcircumferentially right through the chamber before being exhausted bymeans of the fan. Thus, during its travel, the air is gradually heatedup as a result of absorbing the heat given off by the refractorysupporting structure which is thus kept cool by the air.

One embodiment of the present invention is illustrated by way of examplein the accompanying drawing in which:

FIG. 1 is a side elevation, partly in section, of the melting furnace ofthe invention, and

FIG. 2 is a section through the furnace on the line AA of FIG. 1.

Referring to the drawing, it will be seen that the melting furnace isconstituted by a crucible 1 supported at its periphery 2 by a gas-tightrefractory structure 3. This supporting structure encloses thecombustion space 4, a burner 5 being disposed at the bottom 6 of thestructure and a duct 7 for exhausting the burnt gases being located atthe side thereof.

It will also be seen that the furnace has a double wall 8 which definesa chamber 9 which extends around and above the refractory supportingstructure 3. This chamber is provided with a duct 10 which is equippedwith a fan 11 and is connected to an exhaust line 12; the chamber 9 alsohas an annular air inlet 13 extending around the periphery 2 of thecrucible, and a lateral air inlet 14.

The double wall 8 of the chamber 9 has a lateral outer wall 15. Thechamber 9 has a cover 16 which is preferably made of metal.

The lateral wall 15 of the chamber surrounds the lateral surface of thesupporting structure 3 and rests on a protruding portion of the base 6of the supporting structure.

The cover 16 has an outer downwardly extending lip 17 which caps theupper portion of the wall 15 and an inner downwardly extending lip 18terminating near the periphery 2 of the crucible.

The partition 19 which closes off the chamber 9 separates the lateralair inlet 14 from the duct 10.

The crucible 1 is of conventional design; Its wall which is made of asuitable refractory material is of cylindrical form on the outside andis rounded towards the base.

The refractory supporting structure 3 is of cylindrical form andsurrounds the outer side wall of the crucible. The supporting structurehowever extends downwardly to a point much lower than the base of thecrucible and it defines a cavity below the latter.

The supporting structure is made up of refractory bricks, and theassembly of bricks is reinforced by metallic elements 20 which extendfrom the base 6 of the structure to the periphery 2 of the crucible.These elements which are uniformly distributed around the structure areembedded in the refractory composition and also perform the function ofsupporting the crucible on their upper protruding portions.

As can be seen in the drawing, the entire furnace rests on aconstruction, the upper surface of which is square.

The burner 5, disposed at the bottom of the structure 3, is fed througha pipe contained in this construction.

' This burner is selected to suit the fuel used which may be eitherliquid or gaseous.

After having heated the assembly consisting of the crucible and thesupporting structure, the gases of combustion are directed towards theexhaust duct 7 and may then be filtered.

The annular air inlet 13 takes the form of a narrow gap. The lateral airinlet 14 on the other hand is constituted by a row of circular aperturesarranged at equal distances apart along a generatrix of the lateral wall15 of the chamber 9. It will be understood that the apertures formingthis inlet can be of any other shape.

The partition 19 that closes off the chamber 9 is generally of metal. Itextends along generatrices of the lateral wall 15 and the lateral wallof the supporting structure so interconnecting these walls, and isdisposed near the apertures forming the lateral air inlet 14. The fan11, secured to the upper portion of the lateral wall 15 is thus shut offfrom the apertures forming the lateral inlet.

The fan is of a conventional type and is so rated that the amount of airthat it draws in ensures that the furnace is efficiently cooled and thatthe gases given off by the crucible charge are completely exhausted.

The fan is started up while the charge is being melted. It sets up apartial vacuum in the annular chamber into which air passes through thelateral inlet 14 and the annular inlet 13.

The air passing through the lateral inlet 14 is forced to travel rightthrough the entire chamber in order to reach the fan, and is displacedtangentially to the walls of the chamber. Since these walls are hot theair becomes heated upon contact with them and so keeps them cool. Sincethe apertures constituting the lateral inlet are disposed at equaldistances apart along a generatrix of the lateral wall of the chamber,the air-stream extends over the entire volume of the chamber in auniform manner. The lower portion of the chamber is clearly the hottestsince it is nearest the source of heat. The air introduced into thisportion is therefore additionally heated.

The air passing through the annular inlet contains a large amount of thegases liberated in the crucible.

The partial vacuum within the chamber 9 is such that the gases liberatedat all points on the upper surface of the charge are all drawn throughthe inlet 13 into the chamber. 1

It should be mentioned that these gases are mixed with the circulatedcooling air introduced into the upper portion of the chamber. However,these gases which are hot interfere very little with the cooling of theupper portion of the chamber which is not so hot as the lower portionand which therefore requires less cooling.

The air leaving the annular chamber 9 may of course be filtered uponissuing from the fan 11 and before being passed into theatmos'phere.

It will thus be seen that the melting furnace of the invention can bereadily cooled and that the gases from the crucible are exhausted at thesame rate as they are formedwith the aid of the annular chamber providedaround the refractory structure supporting the cruci-.

ble. Thus the use of a hood is no longer necessary and the temperatureobtaining in the area around the furnace is reduced.

I claim:

1. An improvement for a melting furnace of the type that includes acrucible, a gas-tight refractor-y structure surrounding the periphery ofthe crucible, and means for heating the crucible, the improvementcomprising a wall spaced apart from theouter surface of the refractorystructure, the wall surrounding the refractory structure along the sidesand top thereof to form a chamber extending at least around and abovethe refractory structure, outlet means in the wall through which gas inthe chamber can be withdrawn, first and second inlet means in the wallcommunicating with the outlet means, the first inlet means comprising'aspace between the upper periphery of the crucible and the wall throughwhich gas emanating from the crucible can flow, the second inlet meanscomprising an opening in the wall through which gas can enter thechamher.

2. The improvement in claim 1, wherein the chamber includes (a) alateral outer wall resting on a base, and (b) an annular cover which hasan outer downwardly extending lip which caps the lateral wall and aninner downwardly extending lip which terminates near the periphery ofthe crucible.

3. The improvement in claim 2, wherein the second inlet means isdisposed near the exhaust means, and the chamber includes partitionmeans therein between the.

therebetween.

1. An improvement for a melting furnace of the type that includes acrucible, a gas-tight refractory structure surrounding the periphery ofthe crucible, and means for heating the crucible, the improvementcomprising a wall spaced apart from the outer surface of the refractorystructure, the wall surrounding thE refractory structure along the sidesand top thereof to form a chamber extending at least around and abovethe refractory structure, outlet means in the wall through which gas inthe chamber can be withdrawn, first and second inlet means in the wallcommunicating with the outlet means, the first inlet means comprising aspace between the upper periphery of the crucible and the wall throughwhich gas emanating from the crucible can flow, the second inlet meanscomprising an opening in the wall through which gas can enter thechamber.
 2. The improvement in claim 1, wherein the chamber includes (a)a lateral outer wall resting on a base, and (b) an annular cover whichhas an outer downwardly extending lip which caps the lateral wall and aninner downwardly extending lip which terminates near the periphery ofthe crucible.
 3. The improvement in claim 2, wherein the second inletmeans is disposed near the exhaust means, and the chamber includespartition means therein between the outlet means and the second inletmeans for blocking the flow of gas between them along the closestdistance therebetween.